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Safeguarding Your Eyes Against Red Tide – By Katherine Flynn, OD


Florida Fish and Wildlife defines it as a harmful algae bloom with higher-than-normal concentrations of a microscopic organism. A Red Tide can last as short as a few weeks or, in extreme cases, longer than a year. The species that causes most Red Tides is Karenia brevis (K. brevis).

Many Red Tides produce toxic chemicals that impact marine organisms and humans. Wave action breaks open the organism that causes Red Tide, K. brevis, and toxins are released into the air. This can cause respiratory irritation and it can worsen existing conditions such as emphysema or asthma. Fish and other aquatic creatures experience oxygen deprivation during this time and perish. When they wash ashore, there is often a highly unpleasant smell along with airborne irritants.

Some people believe that Red Tide is being worsened by urban and agricultural runoff, although typically Red Tide develops 10-40 miles offshore and is pushed toward the coast by waves and wind.



Aside from an unpleasant smell at the beach or near the coast, the Red Tide brings hundreds and even thousands of dead fish. The air also contains the toxins from K. brevis from the waves and together this makes for an unpleasant experience. Many people report experiencing one or more of the following symptoms during Red Tide:

  • Nausea from foul odor
  • Difficulty breathing
  • Coughing
  • Sore throat
  • Itchy, watery eyes
  • Runny nose/sneezing
  • Redness and burning in eyes
  • Irritated skin/rash
  • The feeling of an allergic reaction


While Florida Fish and Wildlife says it’s safe for most healthy people to swim in Red Tide, it’s always recommended to wear goggles when swimming in any body of water. During times when there is excessive bacteria in the water, the best course of action is to stay out of the water or avoid submerging your head. You may want to consider hitting the pool instead of the beach for your water fun.

Always wear polarized sunglasses to the beach (and outdoors).

As a precaution, you can use preservative-free artificial tears to flush your eyes before and after spending time at the beach.

Avoid touching your eyes.

If your eyes become irritated, wash your face and instill additional preservative-free artificial tears for comfort. You can also lightly apply a cool compress or gel pack to soothe your eyelids and the surrounding area. If irritation persists or worsens or if you experience any additional symptoms or visual changes then we recommend you contact your eye care provider.


Dr. Katherine Flynn is is a board-certified optometric physician specializing in primary medical eye care. She has been with St. Luke’s since 2004 and she sees patients at our clinics in Tarpon Springs, Tampa and St. Petersburg.

For current Red Tide status information visit the FWC updates page